Step 1: Understanding general offers.
A general offer is made to the public at large, and anyone fulfilling the condition can accept it. However, knowledge of the offer is essential.
Step 2: Case law.
In the famous case of \textit{Lalman Shukla v. Gauri Dutt}, it was held that acceptance without knowledge of the offer does not constitute a valid contract.
Step 3: Conclusion.
Thus, for a valid general offer contract, the acceptor must know of the offer before acceptance. Hence, option (b) is correct.